An internal combustion engine for a motor vehicle generally includes an engine block defining at least one cylinder accommodating a reciprocating piston coupled to rotate a crankshaft. The cylinder is closed by a cylinder head that cooperates with the reciprocating piston to define a combustion chamber. A fuel and air mixture is cyclically disposed in the combustion chamber and ignited, thereby generating hot expanding exhaust gasses that cause the reciprocating movements of the piston. The fuel is injected into each cylinder by a respective fuel injector. The fuel is provided at high pressure to each fuel injector from a fuel rail in fluid communication with a high pressure fuel pump that increases the pressure of the fuel received from a fuel source. Operation of the internal combustion engine is generally controlled by one or more electronic control units (ECUs) operably coupled to an array of sensors and actuators associated with the internal combustion engine.
Balanced combustion within the plurality of cylinders of a typical internal combustion engine is important for reliable, low vibration, emission-compliant operation. A number of factors can introduce variability into the cylinder-to-cylinder and cycle-to-cycle combustion process. Factors affecting cylinder-to-cylinder combustion variability include: mechanical construction such as stroke length, head and piston heights, gasket and ring size, camshaft profile, fuel manifold, wave harmonics, etc.; engine and component condition such as worn rings, weak lifters, leaking fuel valves, spark plug and ignition coil degradation (for spark ignition engines), etc.; and combustion controls such as air/fuel ratio, ignition timing, engine cooling, etc.
The fuel injection system under the control of an ECU typically operates under closed-loop, integral feedback control, which can compensate for the foregoing factors that contribute to cylinder imbalance. However, during transient maneuvers such as cranking, high load/acceleration and the like, cylinder balance may be degraded during and following the transient maneuver as the closed-loop integral control does not anticipate the transient maneuver and takes time to converge. During this period of cylinder imbalance there exists the potential for adverse engine vibrations and emissions.
Accordingly, it is desirable to improve cylinder balance within an internal combustion engine especially during and following transient maneuvers.